The invention relates to a device for the granulation of melting and softening materials, more particularly plastic materials, comprising a flash groove in which the material to be granulated is carried and a feedway to the flash groove through which the pressure medium under pressure is intermittently introduced as discrete amounts into the flash groove, whereby the material flow of the material to be granulated is subdivided by volume displacement into discrete portions, i.e., granules. The intermittent introduction of the pressure medium into the flash groove is controlled by the periodic opening and closing of a valve.
Examined West German Patent Application No. 15 48 912 into discloses a device for the separation of flowing media discrete, successive sections which are separated from each other by injecting sections of another medium that is immiscible with the medium to be divided. For this purpose, both media are first carried through separate lines to a junction where the dividing medium is injected from one side into the line carrying the medium to be divided. For this purpose, the dividing medium is compressed via a pulsating dosing unit into a feed line from which it is injected at the junction into the medium to be divided. Because of the admission of the dividing medium by means of the feed line, there may arise in this feed line, particularly at high pulse frequencies, undesirable resonances or reflections that can interfere with the exact rhythmic injection of the dividing medium, so that the precise division of the medium to be divided is not assured. Moreover, turbulences may arise due to the lateral injection of the dividing medium in the junction area, which also deleteriously affect the precise division of the medium to be divided.
Furthermore, U.S. Pat. No. 4,151,251 specifically describes a process for the manufacture of plastic granules in which the plastic granules are produced by intermittent admission of a coolant into a passage carrying a plastic melt. Preferably, water is to be used as the coolant. The coolant is admitted through sintered porous metal over the surface of which the plastic melt is passed. Because of the intermittent admission of the coolant, the plastic melt repeatedly comes into direct contact with the sintered metal in the pauses between admissions. The contact between the plastic melt and the sintered metal poses the risk that small amounts of the plastic melt enter the sintered metal, remain there too long, and thus crack, as a result of which in one respect the plastic melt is repeatedly contaminated and deleteriously affected and the particular orifices concerned in the sintered metal are plugged. Furthermore, the use of the sintered metal requires the admission of highly purified water, because contaminations in the water used as the coolant can continuously clog the sintered metal. Finally, insertion of the sintered metal into the coolant supply line is not advantageous because a considerable pressure drop occurs at the sintered metal which causes a flattening of the sharp sides of the individual water hammers during the intermittent admission of coolant.